To compare real-life performance
we shot the same scene with the EF 17-40mm and EF-S 18-55mm lenses within moments of each other using
a Canon EOS 400D / XTi at f8 in Aperture Priority mode.

The 400D / XTi was set to Large Fine JPEG mode and the Standard Picture Style. The
crops are taken from the originals and presented here at 100%.

The image left was taken with the Canon EOS 400D / XTi using the EF 17-40mm at 22mm
f8; the original JPEG measured 4.15MB.

At first glance, the two lenses appear to deliver similar-looking results, but upon closer inspection some differences emerge. In the top row of crops showing the mountain ridge, the EF 17-40mm looks a little sharper on fine details like the areas of snow - these also show a little coloured fringing on the EF 18-55mm crops, but it's pretty close.

The middle row of crops taken from near to the centre of each lens appear virtually identical, but the biggest difference can be seen in the final row of crops. Here the EF-S 18-55mm sample is quite soft in comparison, losing the finest detail in the branches and foliage.

Ultimately in this test with both lenses closed to f8, it was quite a close result, although as you'll see over the following pages there are several areas where the EF 17-40mm comfortably out-performs the budget kit lens.